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News, reports and analysis on law and politics in the UK

Cannabis and Mental Health

Cannabis has caused much controversy in the last decade or so. In the UK it has been yo-yoing between class C and B (it is currently class C, but there is a review on its classification to decide whether to move it back to Class B or not). In amongst all of this, there are regular calls for its legalisation as it allegedly causes no harm whatsoever. The effects of the drug are still, to a degree, unknown. However, it is clear that one cannot truly hold the view that it causes no harm to anyone; ever.

There is a large bank of evidence to support the view that Cannabis has a detrimental effect upon one’s psychiatric well-being. The bulk of the evidence does not support the view that cannabis causes mental illness in the first place, but research has strongly suggested that there is a clear link between early cannabis use and later mental health problems in those with a genetic vulnerability.

There is a particular issue with the use of cannabis by adolescents (adolescent usually describes a patient between the age of 12/13 and 17/18). Adolescents that use cannabis daily are around five times more likely to suffer depression and anxiety in later life. Adolescents, it would appear, are more likely to use cannabis than people of other age groups.

One other psychiatric condition that cannabis use is often associated with is Schizophrenia. Three major studies followed large numbers of people over several years, and showed that those people who use cannabis have a higher than average risk of developing schizophrenia.

Research has also discovered that if a person start’s smoking Cannabis before the age of 15, a person is 4 times more likely to develop a psychotic disorder by the time they are 26.

The three major studies into Cannabis use and Schizophrenia mentioned above also discovered that the more cannabis someone used, the more likely they were to develop schizophrenic symptoms.

Recent research in Europe, and in the UK, has suggested that people who have a family background of mental illness – and so probably have a genetic vulnerability anyway – are more likely to develop schizophrenia if they use cannabis as well.

Why should adolescents be particularly vulnerable to the use of cannabis? No one knows for certain, but it is possible that it has something to do with the fact that the brain is still developing during these years (up until the age of 20 in fact.) A massive process of ‘neural pruning’ is going on. This is rather like streamlining a tangled jumble of circuits so they can work more effectively. Any experience, or substance, that affects this process has the potential to produce long-term psychological effects.

Another issue which those who advocate the legalisation of cannabis appear to focus on, and try to claim does not exist, is ‘Cannabis Psychosis’. ‘Cannabis Psychosis’ is a short-lived psychotic disorder that seems to be brought on by cannabis use but which subsides fairly quickly once the individual has stopped using it. Research fro Denmark suggests that it does exist.

The Danish research found that three quarters had a different psychotic disorder diagnosed within the next year and nearly half still had a psychotic disorder 3 years later.

So, it also seems probable that nearly half of those diagnosed as having cannabis psychosis are actually showing the first signs of a more long-lasting psychotic disorder, such as schizophrenia.

There is also some debate surrounding whether Cannabis is addictive or not. It has some of the features of addictive drugs such as tolerance and withdrawal symptoms. The symptoms of withdrawal produce about the same amount of discomfort as withdrawing from tobacco.

So with only scraping the surface it can be seen that Cannabis has an effect on a person’s Psychiatric wellbeing. With roughly 1 in 4 people in the UK suffering from mental health problems at one stage in their life avoiding cannabis – especially in teenage years – is something that is well advised.

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